Fair Value Measurements - Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis) (Details) - Nonrecurring - USD ($) $ in Millions	Jun. 30, 2021	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 503	$ 921
Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	140	186
Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	2	54
Commercial loans and leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	313	569
OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	6	18
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	7	14
Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	34	10
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	1	70
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	502	884
Level 3 | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	140	186
Level 3 | Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	2	17
Level 3 | Commercial loans and leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	313	569
Level 3 | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	6	18
Level 3 | Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	7	14
Level 3 | Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	34	10
Level 3 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	70
Level 3 | Comparable Company Analysis | Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	2	16
Level 3 | Comparable Company Analysis | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value		70
Level 3 | Appraised Value | Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value		1
Level 3 | Appraised Value | Commercial loans and leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	313	569
Level 3 | Appraised Value | Consumer and residential mortgage loans | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	140	186
Level 3 | Appraised Value | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	6	18
Level 3 | Appraised Value | Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	7	14
Level 3 | Appraised Value | Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	$ 34	$ 10